Method of applying a discontinuous coating to paper



March 1952 P. A. SNOWMAN, JR

METHOD OF APPLYING A DISCONTINUOUS COATING TO PAPER Filed Aug. 5, 1948 3 Sheets-Sheet l INVENTOR. PAUL A. jmovvr mm JR.

TRNEYS.

in AT Fill];

P. A. SNOWMAN, JR

METHOD OF APPLYING A DISCONTINUOUS COATING TO PAPER Filed Aug. 5, 1948 March 18,1952

3 lSheets-Sheet 2 0000 O0 ww ooooooooo 0 0000 0000 O0 OO www ooop o 00 0 00 O 09000000 4 DO. m 00000 30000 w 0 00000 0 0000 0 0000 00000 00000 000000 00000000 000000O 00000000 OOOO OQOO 0000 0000 0000 D000 COCO Z 2 2 915. APPLJCATQR ROLL.

INVENTOR.

PAULA.5NOWMAN JR. UMJ.,W 1 49. M ATTORNEY5.

March 18, 1952 p A, SNQWMAN JR 2,589,302

METHOD OF APPLYING A DISCONTINUOUS COATING TO PAPER Filed Aug. 5, 1948 3 SheetsSheet 3 INVENTOR. PAUL. A .SNQWMAN JR.

LA. ATTO RNEVS.

Patented Mar. 18, 1952 METHOD OF APPLYING A DISCONTINUOUS ooa'rnvo T0 PAPER Paul A. Snowman, .112, Glen Ridge, N. J assignor to North American Paper Process Company, Inc., New York, N. Y., a corporation of Delaware Application August 5, 1948, Serial no. 42,656

- 1 This invention relates to the coating of papgr, and more particularly to novel methods forlapplying to paper a coating of extremelysslight weight. The invention also relates to methods'ifor applying-"to; paper such a coating and creating thereupon a novel glazed skin or film. Furthermore, the invention relates to the products'of such methods. .iiv The invention makes possible the production of a paper which gives the appearance of being uniformly-and attractively coated, yet the coating film'isZ-discontinuous in that according a uniform, predetermined pattern there are fine areas which are uncoated separated by areas of very small dimension which are coated. Thedis- 'continuous coating is constituted by, it} example, fine mounds of coating material offiiiite height. 'The fine coated and uncoatedare'as, respectively. are of such small dimensions that they are not independently readily noticeable as viewed with the naked eye at the intended distance for vision and consequently the paper pre- 3 Claims. (01. 117--38) sents the appearance of being entirely uniform.

The intended distance for vision with respect to a sheet bearing printing of normal sizeis approximately fourteen inches. However, since a considerable percentage of the total area is not actually coated with a coating mixture this appearance of a uniform coating is achieved by the .use of a substantially smaller amount of, such mixture than would be required to provide-a 'continuous coating having good printing qualities.

It has been impossiblein the past satisfactorily andeconomically to coat certain grades ofpaper, particularly the lower grades. One reason for this is that certain lower grades such as kraftl have highly irregular surfaces containing hills and vallys of accentuated character as compared to other grades. The coating apparatus and methods of "the prior art are unable uniformly to spread-the coating mix upon both the high and the lows rfaces, It has not been possible in the past '-i io apply a satisfactory'lightweight coating, for example, of'the order of two to three pounds of coating per ream (26',' x 38"-500 sheets) per side, ,by conventional coating methods, which coating will appreciably improve the appearance and/or the printing qualities of the sheet.

Past apparatus and methods have produced coatings. 'for example, wherein peaks or ridges kientuated'the surface irregularities of the paper 2 and have been incapable of applying a lightweight coating uniformly.

According to the present invention, a coated paper and method for producing same are provided for satisfactorily avoiding theabove noted difficulties.

One form of the invention illustrated in the accompany drawings and in the description, by way of example, comprises a novel method for applying a coating by intaglio means to a travelling ,web of sheet material, whereby the above-described discontinuous fine coating is achieved, thereafter the coating is dried, a skin is formed thereon and glazed by means of a highly polished, moving surface such as a heated glazing-drying roll or glaze roll. Said coating is applied in accordance with a uniform, minute pattern formed upon an applicator or coating roll. Suchpatter-n can comprise, for example,-a minute grid design or a plurality of minute, uniformly spaced, separate depressions formed in the surface of the applicator roll. A backing roll is employed with the applicator roll, these two rolls being urged together at a desired pressure and the travelling web passing therebetween. A fountain roll, which is partially immersed in a bathof coating mix, is preferably in sufiiciently close contact with the applicator roll to transfer the coating mix to the latter. 1 In order to scrape off of the applicator roll all of the coating mixexcept that which is contained in said depression, a. doctor blade is employed whereby said roll can deposit directly upon, the travelling web a plurality of minute portions or mounds ,of coating -mix, thus forming areas of very fine dimension which are coated and which are separated by areas of very fine dimension which are uncoated. The travelling web is next subject to said heated glazing-drying surface to form said glazed skin. One of the main reasons for subjecting the travelling web to such a surface is to produce a glazed sheet which meets the requirements, for example, of paper adapted for rotogravure printing and the like. After the web has passed over the heated glaze roll it can be sub- Jected to a plurality of drier rolls as desired.

Paper which, for example, is adapted for rotogravure printing should have as nearly a perfect plane surface as possible. Such a surface has been achieved with continuous coatings in the past, but heretofore it has been impossible to provide such a surface having a discontinuous coating. The novel method herein described produces a coating of a lighter weight than heretofore possible at a cost lower than heretofore attained and yet such a surface, for practical rotogravure purposes, is substantially a perfect plane having a glazed skin superposed upon said fine discontinuous coating.

A sheet adapted for rotogravure printing, in

addition to having the above-mentioned smooth surface, should have a hardened skin or surface in order to achieve the desired printing reproduction qualities. scribed provides such a hardened skin upon the top surfaces of the mounds and upon the intervening uncoated areas. The latter areas are provided with an adequate hardness by virtue of (a) the fanning out or dispersion of the binder which tends to permeate the paper -b'e-' neath such uncoated areas; and (b) the fiowing or migrating of some of the binder fromthe mounds of coating mix onto and over the uncoated areas. 7

When said travelling web is pressed against the above-mentioned heated glazing-drying-surface or glaze roll, the fine mounds are-pressed while-in a plastic state thereagainst, thereby tending to level and press same into the paper, but .the

pressing is accomplished in such a manner that the discontinuous nature of the coating is-preserved. The heated glaze roll induces first a migration of the-binder out of the fine mounds whereby such binder flows to the top surfaces of the-mounds and also onto the fine uncoated areas therebetween. Secondly the heated glaze roll causes a drying and hardening of said binder over the top-surfaces of said mounds and in said uncoated areas whereby the above-mentioned glossy hardened skin is created. Thus, a-binder which-flows out of a given fine mound and onto a-contiguous uncoated area may there merge with binder from adjacent mounds, thereby forming said substantially continuous skin over all of the mounds and areas intervening therecoating which is provided with a substantially continuous glazed hardened skin which extends over the mounds and over the intervening uncoated areas to create a substantiallyplane glazed surface.

It hasbeen mentioned above that in the past,

many grades of paper, particularly lower grades such as kraft, havenot been coated because of -the'high'cost and excessive added weight of the coating.

Many such lower grades of paper have badlyneeded to be coated in order, not only to enhance the appearance and to improve the printing qualities thereof, but to increase the abrasion resistance thereof. This latter quality -is'ofparticular importance with respectto such papers as kraft. The novel methods defined herein can also be used to advantage to apply certain materials to the paper to change the physical properties of the finished sheet, for example, (a) to control wax or oil adsorption and/or (b) as above mentioned, to increase abrasion of scuff The novel method herein deresistance. Also due to the very efficient method of application and distribution herein disclosed, materials which heretofore have been considered too costly, can be economically applied, and materials which are of such a thixatropic nature that even coatings or applications cannot be obtained by methods heretofore proposed, can be easily obtained by a practice of the present invention. Thixatropic as employed herein refers to the property of a material of becoming fluid when force is exerted thereupon, and of becoming nonflowable when such force is removed. The use .of a mix having a desired thixatropic nature assists in preventing coalescence of the mounds.

Moreover,- materials which are sensitive to a change in pH and-which cannot be applied commercially. topaper because of residual acidity in the sheet, cari'how be effectively applied over long -periods at high speeds. For example, in connection with the application of non-coating mixes such as surface sizing; in prior methods an fexcessof such material has been allowedto .collectat. the inputto the so-called inip betweenthe application roll and the backin roll. Residual, acid ions in, the paper may; a fiect chemically such excess and portions of thela tter so affected; fall backinto-the reservoir therefor and cause the pH of the material in the reservoir to diminish t o or-approachthat of the paper. This can spoil the applicationof the material, for mple. y au i a u.mm. n th eofior; i casein is present a precipitation thereof; may occur or.--if an emulsion is desired in such material-the emulsion may be broken, I

The invention in another aspect thereof comprises another novel method which will justify and make commercially feasible the coating of .low grade papers, and which will overcome the above mentioned difiiculties regarding the change in pH The novel method will produce a novel product embodying the above-mentioned desired characteristics of enhanced. appearance, high abrasion resistance, and improved printing qualities. Such invention is constitutedby'the above-described method and .product with the distinctions:

(1) The 'glaze'roll and its effects are eliminated; and

(2) The fine discontinuous; coatingis substantially dried entirely before the fine mounds thereof are pressed against a drying surface.

Thus the coating comprises a'plurality of fine mounds of finite height separated byminute'uncoated. areas, the mounds being not readily noticeable at intended-distances for visioni' and giving the appearance, of a continuous coating.

The application of the coatingas a direct print from an intaglio applicator; roll substantially eliminates coalescence ;of the discontinuous coating whichnormally might occur 'ifan offset roll were employed. This preserves; the discontinuous nature of the coating. It is important to preserve this quality because itenables the applicator roll to apply a coating with a uniformity of pattern which normally would be impossible. The applicator roll, at the high or unpittedareas thereof, is in'direct'contact with the surface of the travelling web whereby the coating is laid upon the web in a manner which is not affected by the usual variations in thickness or sur'face contours of the web. The factthat'the'backing and applicator rolls are urged together ata de- 'si'redpressure assists injthe laying 'down' of the hills or H mounds-in this manner "because either purposes of illustration onlyand are not intended -as a definition of the limits of the invention,

reference for this latter purpose being had to the appended claims. 1 it In the drawings: I Fig. l is a side elevation illustrating somewhat schematically one form of apparatus for carrying out one form of the present invention;

Fig. 2 is a detailed view of a portion of an applicator or coating roll' used with the present invention, the surface formation being shown I greatly enlarged; I

Fig. 2a is a greatly enlarged view, of a fragment of a paper web coated in accordance with th v .invention by the feed roll of Fig. 2; i

; Fig. 2b is a greatly enlarged View of a fragment of a paper web bearing a discontinuous coating of uniform pattern of the grid type having substantiallysquare mounds, the coating being applied in accordance with the present invention;

Fig. 3 is a greatly enlarged fragmentary detailed view of a paper web passing between a coating roll and a backing roll;

v Fig. 4 is a greatly enlarged cross-sectional view of a paper: web having mounds of coating mix v applied thereto in accordance with one form of the invention, the mounds illustrating the porous structure which is obtained by allowing the coating to dry without the application; of anysub- 6 tional manner by a couch roll I9 and supported by a breast roll 20. Suitable straps, as atll, are provided to keep the stock within the edges of the wire I8. Suction boxes 22 are employed which act in a well knownmanner beneaththe upper run of the screen IB and the paper fibres are laid down on said screen by a dandy roll' '2f3 and a couch roll 24 also in a conventional man- A web of paper 25 issues from between the couch rolls 1%! and 24 and passes to the press rolls l4 above mentioned. Suitable. feltnssuppoft blankets (not shown) can be employed for guiding the; web relative to the press rolls I14.

Thereafter theweb 25 passes through-zthe drier I5 and thence to the breaker stack Hi from which it issues in a dried or partially dried form to the coating unit I0.

The breaker stack IB should not compress the web to any appreciable extent but performsonly its. conventional function of relieving" drying strains and smoothing out cookies in the sheett j It will be understood, of course, that power is applied by suitable gears, shafts .and othe mechanism to the rolls described herein. 1'

The web 25 passes from said-stack lfiover an idler roll 2a to the coating unit: Ill, The latter is constituted by a backing roll 21 and anappli- :a suitable slotted support member tlwwhereby stantial compacting force, such as in calenderr Fig. 5 is a still further enlarged. cross-sectional .viewof the web and vcoating shown in1Fig. 4' 'after the same has been glazed in.-accordance with another form of the invention; and

Fig. 6 is a side elevation illustrating schematically one form of apparatus for carry-ingout the- :invention and for applying the coating, ,as shown 15 and abreaker stack l6. Five drier rolls [5a are shown, but any desired number can beemployed, depending, for example, upon the desired dryness of the web prior to coating, the "grade and weight of the paper, and the speedof the web. For example, with certain typesof kraft,

it may be desirable for the web to be relatively damp in order to assist in the application of the discontinuous coating,. the relatively dampweb,

of course being more easily pressed to a uniformthickness between a coating roll and;a backing roll.

Paper buIk or stock is fed to theFourdrinier unit from head box 11, the pulp passingto'a wire screen [8 which can be driven -in,a conventhe roll 2'! can be shiftecltoward or awayfrom the applicator roll 28. A hand wheel and threaded shaft 32 at each extremity of the roll 21 provide ,means for adjusting the compression .of springs 29. r A fountain roll 33 is partially immersed in a bath of coating mix 34 contained in.;a receptacle 35. The fountain roll 33, in the form shown,

(1) Clay Coating starch 20.1; Neutral white soap .02 Wate 99.: (2) Clay e 100;:-

Casein' e .15. Ammonia (26 Baum) .75 Water 94.5

The terms ,coating mixture and.coating material" as employed herein refer to such, substances of the aqueous mineral variety: -The term binder as employed herein lexcludes'such substances as oils.

The Weight of the coating applied per unit area, of course, is a function of the number and size of depressions of the applicatorroll. The percentage of solids in the coating mixwill also affect the weight of coating applied and I have found that good results are obtained when the coating mix contains'solids at the highest practical percentage. This speeds the drying of the :.coating and reduces the tendency thereof .to

uzoalesce and also become distorted.

:indicated iin Fig. .2, the applicator ;.roll 28 zisgprovidedupon the-surface thereof with axplu- .srality aof uniformly-spaced .and uniformly "ar- :ranged :minute .depressions 28a which, .for vex- ;ample man be :knurled or .engraved .or etched therein.

I have found that the discontinuous coating -.of uniform patternisibetter .applied by the. in-

xtaglio" method, :that .as a .direct :print :from

anrintaglioroll, :because of the. substantial avoid- .ance .of. coalescence .ofzthe coating. .This is.1importantbecausea coalesced coating of this gen- .eral ..-character .cannot be so uniformly "applied,

:iisssubiect to streaking,..and furthermore, :often permitsunsightly.defects1toappear in the finished sheet caused, for example, by protruding fibres :and shives.

v."Asshown:in Fig. L2a,=thecoating is applied-to v the-weba25*without coalescence, the pattern be' ing clearly preserved and comprising a plurality of :uri'iformly-rspacedhills or mounds which, for

example, are substantially circular when viewed fromfabove. The'hills or mounds, instead of be,- ing inithis shape, can'be substantially square and arranged in agrid pattern, asshown in Fig. 2b. Any substantially uniform arrangement -of sub.-

sstantiallyuniform*hillsor mounds of-this minute :chara'c'ter cairbe empioyed. It is understood that; theviews of the discontinuous coatings'in Figsgj 2a and Zbare greatly enlarged and that'normally; :the 'hils ormounds thereof are not readily dis? =cernible, as have been above described. The agigrega'te of the coated areas is preferably about thirty-five to seventy-five-per cent. of the area of the'coated sideof the web.

Further, with respect "to the size of the coated areas or mounds of coating material, I have found that the maximum length --or diameter thereof should not exceed about .0080 inch, and" the height after drying is preferably about .0005 inch," Regarding shape, any circumscribed figure "can'be used. As to spacing, the distance between;

two coat-ed areas (having no intervening coated areas; therebetween) should not exceed about .0080i inch nor be less than about .0020inch. Of

course, it is possible to apply -mounds of the maximum length or diameter separated by the; -.minirr'1um distance. The minimum spacing -di-;

mens n of about .0020 has reference to the disto the nearest coated areas. 'If the abovemenft ned limits of dimensions are employed,

eaolifi'coated and adjacent uncoated area will be ofsu'lch size that they will subtend a visual angle less than that required for conscious resolution :by tlfeunaided eye at a normal distance, forexample,.fourteen inches, at which the surface is to be viewed.

After the paper web has received the fine discontinuous coating from the coating unit I0, the coated side thereof is passed over the heated ,giaze :roll H which, for example, is provided ,gration of the binder outthe fined mounds of l acoatingrmix to iorm;arskin over'the entire surrifacegof :the :sheetz-as: shown at 1 3 I .(Fig. 5) Thus :the zbindenis caused tomigrate to the top'sur- .facero'f :thezmounds and also onto the fine-uncoated .-.areas ".therebetween. A binder which ilows :out .ofa given; fine mound .and onto. a 'contiguous uncoated area may there merge with .hinderfromadjacent mounds, thereby forming ..'said1.sub'stantially.rcontinuous skin.

13) .Theiiheat :of .the glaze roll causes a con- :traction of the paper web passing thereover .which :assists in pressing the paper web upon itheglaze roll-and which also :assists in forming :a substantially level surface by forcing paper fibres above their normal levels between the mounds as at 2512 "(Fig 5) and simultaneously the mounds of coating mix shrink due'to a loss of water caused by heat while'under pressure. .Asubstantially level "sheet isproduced in-so far as practical printing requirements are concerned. There-is a smaller quantity of coating material required to fill in the valleys between the mounds thanwould be necessary if such contraction and such upheaval did not occur. The migrating binder tends to migrate intothe paper beneath such uncoated areas, 'thereby assisting in hardening same, and, as above mentioned, a small amount of migrating binder will flow onto such uncoated areas and thus will tend to fill in'the valleys'between the mounds to provide a substantially continuous skin.

(4') The thin film of .binder above described is made glossy =or glazed and the pressure applied by the above-mentioned contraction assists in reducing a substantially level glazed and hardened surface.

The solids and the pigments in the coating mix, because of their high viscosity and/or insoluble 'nature,'undergo no migration or undergo :such a'smallamount as to be of no significance. This assists in maintaining the discontinuous nature of the coating. The paper fibres are kept in a partially plastic condition because of water vapor escaping through the web during "the rglazing action and thus such fibres are forced'into intimate contact with and thoroughly bound to the fine mounds of coating mixture.

After the web is passed over the glaze roll H, it'preferably is passed over a plurality of drier rolls 38, for --example, three as shown in Fig. 1,, which complete the drying of the paper web. Thereafter the web can be calendered, if

desired, or-can-be wound upon a suitable core.

The novel product of the above-described method is indicated in cross-section in Fig. 5.

The apparatus for carrying out another form of the novel method described above is indicated in Fig. 6 and is substantially identical to the apparatus shown in Fig. 1, with the exception that the {glaze roll H is omitted and (1) the coating is-subjected 'to heat as in a hot air jet, and (2) the uncoatedsideof the paper web,

immediately is passed over the first of a series of drier'rolls 39 of a drier unit 40. shown, five drier rolls 39 are employed. The

In the form drier unit 40 preferably includes means as at t! for directing a plurality of jets of hot air -=upon the coated side of the web. The hot air jet and the first drier'rollsubstantially dry and remove the plasticity of the fine mounds before the latter are pressed against the second drier roll.

' The drier unit accomplishes a complete setting or solidifying of the coating, the solidifica- 131011 being suificiently'complete by virtue of-the aussaaoar hot air issuing from thejets 41- andthe'flrst drier roll 39 to prevent compacting or embeddin of the mounds into the paper web in any substantial amount, a cross-section of such mounds upon the web being indicated in Fig. 4. This latter representation is of the coated web after passing over the last of the drierrolls 39.

Regarding the pressure between the applicator roll 28 and the backing roll 21, relatively light pressure oan exist therebetwecn and thecoating mounds can be appliedpropefly, provided-the web surface is relatively smooth. But if the web surface is wavy and rough, suiiicient pressure should be applied: (1) to compress the web between said rolls to a substantially uniform thickness to insure even disposition ofr-the mounds upon the hills and in the valleys thereof, or (2) to cause the backing roll because of its resilient nature to urge the valley surfaces agairistthe applicator roll. The backing roll '21, as indicated Fig. 3, is preferably of rubber, which'can be of sufficient hardness either to compress the paper web as above described and/or to urge the relatively low surfaces thereof against the coatingroll 28. i

When pressure is applied as in (1) and (2) above, there is a forced penetration of the coating material into and around the paper fibers while such material is in a highly plastic state. This forced penetration occurs in a novel manner by virtue of the forcing of the lip of each depression or cup strongly against the paper whereby considerable pressure is brought about to urge the material into the paper.

Certain types of paper when greatly enlarged in cross-section can appear to have an undulating but relatively smooth surface, as shown in Figs. 3, 4 and 5. The proper compression of the web between the applicator and backing rolls enables an even disposition of the mounds over this entire surface regardless of its undulating nature.

The novel method permits the application of coatings, for example, of a conventional starch or casein variety, in amounts which are substantially less per unit area than heretofore possible. A coating which is approximately one-half to one-third of the weight of minimum coatings pre-. viously possible can be applied by means of the present invention, such a lightweight coating being ofa heretofore unattained low cost and providing abrasion resistance in a high degree.

The uncoalesced coating constitutes only a light burden for the paper, thereby making it unnecessary to have fibres of high strength which heretofore have been required in relatively thin 3'.

papers to support the added load of the coating. The intaglio application under pressure of the discontinuous coating permits of a highly uniform patterned, unstreaked, and generally unblemished coating which is substantially free from defects caused by slight variations in web thickness. Greatly enhanced printing qualities are achieved by virtue of the coating.

In the above-described embodiment of the invention, the application of the coating is applied in the middle of the drier bank of the paper machine. However, the coating can be applied at an earlier point in the drying of the web but not until about eighty per cent of the moisture has been removed therefrom. Of course, the coating also can be applied after the web is fully dry.

Also coatings can be applied to both sides of the stock as a separate operation after the stock has been made in the usual manner, provided thepaper has not been highly calendered; r

While the invention has been described with respectto certain preferred examples which have given satisfactory results, it will be understood. that various changes may be made without de-= parting' from the spirit and scope of the invention as the same will now be understood by those skilled in the art. For a definition of the limits of the invention, reference will be had to'the appended claims.

What is claimed is:

1.. The method for applying a lightweight discontinuous coating of uniform pattern to a traveling web of paper which includes: applying to said web by direct print fine relatively closely spaced but segregated and uniform quantities ofan aqueous mineral pigment coating mix including a binder, water and inorganic filler, said coating mix binder being selected from the group consisting of starch and casein, said mix containing inorganic filler in an amount between about forty-five and seven-tenths and fortyseven and six-tenths per cent by weight and binder in an amount between about seven' and one-tenth and nine and. two-tenths per centby weight, and thereafter While still moisturging the closely spaced but segregated quantities of coating mix against the web by means of a highly polished rotating glaze member traveling at the same speed as the web, with a preselected pressureadequate only to insure uniform even contact, the closely spaced quantities of mix maintaining separateness but being partially flattened against the web, said glaze member being heated to a preselected temperature whereby the heat of the glaze member when contacting such quantities causes portions of the binder to migrate to the surface of such closely spaced quantities of mix and onto the uncoated areas of the web and thereafter are glazed by said glaze member to form a substantially continuous skin over the Web, the discontinuous coating including the residue of said mix after migration of such portions of the binder, the web having coated and uncoated areas of such fine dimension that they are not readily distinguishable at distances for normal vision between about twelve to sixteen inches.

2. The method for applying a lightweight discontinuous coating of uniform pattern to a traveling web of paper which includes: applying to said web by direct print fine relatively closely spaced but segregated and uniform quantities of an aqueous mineral pigment coating mix including substantially one hundred parts clay, twenty parts coating starch, two-tenths part natural ,white soap and ninety-nine parts water, such member traveling at the same speed as the web, with a preselected pressure adequate only to insure uniform even contact, the closely spaced quantities of mix maintaining separateness but being partially flattened against the web, said glaze member being heated to a preselected temperature whereby the heat of the glaze member when contacting such quantities causes portions web, for example, by using two coating units It above described, one for each side.

Coatings can be applied by this method to paper of the binder to migrate to the surface of such closely spaced quantities of mix and onto the uncoated areas of the Web and thereafter are glazed by said glaze member to form a substantially continuous: skin' over: the: web, ,,the;disconitinuous coatin'g including vthe .residue of 'said after migration of: such portions: of ithexbinder;

the webs having coated: and i uncoatedi areas: of such fine "dimensionathat they "are-not .readilyi'dise tinguishable at distancesfor:normalvision be tweeniabouttwelve:tosixteenzinches:

3.1: Thetmethod of applying a: lightweight: dis

continuous. coating: of :T uniform pattern to; traveling: web: of" paperlzwhich includes: applying; to said webby direct print'fine relatively closely spaced but segregated and uniform quantitiesmf an aqueous mineral pigment coatingamixiinclucb ing 1 substantially one hundred parts telaygfifteen parts casein,: seveni-tenths; part1: ammoniaz and;

ninetysfour andion'e-half parts :water; suchzparts: referring? to' weight-,1 and thereafter: whiles: still. moistsurging; the closely spaced butcsegregated; quantities: of coating: against: the" web? by" means of i a highly polished; rotatin glaze .meim

bertraveling'at the same speed as the web; with a preselected pressure" adequate only to'insure' '-}s'aid;.glaze; member: to -form: a substantially: con-e 5 tinuous skin overth'e .web, the discontinuous coat-.-

in'g including the residue of ;'said mix after migration of such'portions; ofithe rbinder;thexweb haw ingv coated 1 and uncoated. areas :of 1 such': fine 1dimension'thatztheygarenot readily distinguishable; m at distances for normal vision between: about twelve to" sixteen inches.

PAULA SNOWMAN, JR;

REFERENCES. CITEDIv i5 The-following referencesare of recordi'inrthe.

file of this: patent:

UNITED STATES PATENTS I; Number Name. Date; 2304.818; Grupe .Dec.;15', ,1942.' 2396,9462 Grupe" Mar. 19;,1946i 2306.287 Grimshaw Aug, 28; 1946 $417,009 Miller Mar. 4.11947 OTHER REFERENCES edn, 1946, page- 190;

hinder-to: migrate" toxthec-suriacer of -.suchclosely: spaced-quantities: of jmixzandhonto the;.-uncoated; 'fa rea's; ofthe web and: thereafter. are: glazed :by;

Ilford Manual of Process Work, L. P. Clerc; 4th" 

1. THE METHOD FOR APPLYING A LIGHTWEIGHT DISCONTINUOUS COATING OF UNIFORM PATTERN TO A TRAVELING WEB OF PAPER WHICH INCLUDES: APPLYINGG TO SAID WEB BY DIRECT PRINT FINE RELATIVELY CLOSELY SPACED BUT SEGREGATED AND UNIFORM QUANTITIES OF AN AQUEOUS MINERAL PIGMENT COATING MIX INCLUDING A BINDER, WATER AND INORGANIC FILLER, SAID COATING MIX BINDER BEING SELECTED FROM THE GROUP CONSISTING OF STARCH AND CASEIN, SAID MIX CONTAINING INORGANIC FILLER IN AN AMOUNT BETWEEN ABOUT FORTY-FIVE AND SEVEN-TENTHS AND FORTYSEVEN AND SIX-TENTHS PER CENT BY WEIGHT AND BINDER IN AN AMOUNT BETWEEN ABOUT SEVEN AND ONE-TENTH AND NINE AND TWO-TENTHS PER CENT BY WEIGHT, AND THEREAFTER WHILE STILL MOIST URGING THE CLOSELY SPACED BUT SEGREGATED QUANTITIES OF COATING MIX AGAINST THE WEB BY MEANS OF A HIGHLY POLISHED ROTATING GLAZE MEMBER TRAVELING AT THEE SAME SPEED AS THE WEB, WITH A PRESELECTED PRESSURE ADEQUATE ONLY TO INSURE UNIFORM EVEN CONTACT, THE CLOSELY SPACED QUANTITIES OF MIX MAINTAINING SEPARATENESS BUT BEING PARTIALLY FLATTENED AGAINST THE WEB, SAID GLAZE MEMBER BEING HEATED TO A PRESELECTED TEMPERATURE WHEREBY THE HEAT OF THE GLAZE MEMBER WHEN CONTACTING SUCH QUANTITIES CAUSES PORTIONS OF THE BINDER TO MIGRATE TO THE SURFACE OF SUCH COLSELY SPACED QUANTITIES OF MIX AND ONTO THE UNCOATED AREAS OF THE WEB AND THEREAFTER ARE GLAZED BY SAID GLAZE MEMBER TO FORM A SUBSTANTIALLY CONTINUOUS SKIN OVER THE WEB, THE DISCONTINUOUS COATING INCLUDING THE RESIDUE OF SAID MIX AFTER MIGRATION OF SUCH PORTIONS OF THE BINDER, THE WEB HAVING COATED AND UNCOATED AREAS OF SAID FINE DIMENSION THAT THEY ARE NOT READILY DISTINGUISHABLE AT DISTANCES FOR NORMAL VISION BETWEEN ABOUT TWELVE TO SIXTEEN INCHES. 